A library is an institution that collects, sorts out and collects books and materials for people to read and refer to. Library is the external storage and selective transmission mechanism of social memory (usually written information). In other words, the library is the storage and diffusion device of social knowledge, information and culture. The professional work of the library is composed of many interrelated work links, which generally includes four parts: document collection, collation, collection and service.

Document collection is the foundation of the whole library work, and document arrangement includes document classification, subject indexing, description and catalogue organization. Literature collection mainly includes the division of stacks (see collection organization), book arrangement (see similar book arrangement methods), collection inventory and document protection. Library service is the work of developing and utilizing library resources. Libraries not only preserve handwritten and printed documents, but also other carrier resources, the purpose of which is to make better use of them.